1. Field of the Invention
This invention relates to a conductive rubber member particularly preferred for a conductive roll or blade which is used to impart a uniform electrostatic charge to a photoconductor of an image forming apparatus such as an electrophotographic copier or printer, or a toner jet copier or printer.
2. Description of the Related Art
A conductive roll of an image forming apparatus such as an electrophotographic copier or printer is required to have non-staining properties and electrical conductivity toward a photoconductor or the like. Thus, conductive rolls formed from polyurethane or silicone rubber have been used. Because of staining properties or electrostatic properties toward a photoconductor or the like, however, proposals have been made for conductive rolls provided with various coating layers, surface treatment layers, or coating tubes on the surfaces of various elastic layers (see, for example, Japanese Unexamined Patent Publication No. 1994-175470 (claims); Japanese Unexamined Patent Publication No. 1993-281831 (claims); Japanese Unexamined Patent Publication No. 1992-214579 (claim 2, [0022], etc.); and Japanese Unexamined Patent Publication No. 2002-040760 (claims)).
Of these prior art documents, Japanese Unexamined Patent Publication No. 2002-040760 (claims) discloses a charging member for which the applicant of the present application filed the application as a low-cost charging member capable of maintaining satisfactory characteristics for a long term. The charging member has an elastic layer comprising an epichlorohydrin rubber base material, and has a surface treatment layer formed by surface treatment with a surface treating solution containing at least one polymer selected from acrylic fluoropolymers and acrylic silicone polymers, a conductivity imparting agent, and an isocyanate component.
To improve the characteristics of a charging roll, the applicant proposed a charging roll having a surface treatment layer obtained by surface treating a rubber layer comprising epichlorohydrin rubber with a surface treating solution containing an isocyanate compound (see Japanese Patent No. 3444391).
However, epichlorohydrin rubber is defective in that its processability is poor. Thus, it is difficult to perform extrusion or injection molding of epichlorohydrin rubber which leads to improved productivity or cost reduction. Even if a plasticizer, a processing aid (factice), etc. are added in large amounts, advanced shaping techniques or various contrivances are required. As a result, a considerably advanced contrivance has been needed to obtain excellent roll characteristics (staining resistance, surface properties, compression set).
The present invention has been accomplished in the light of the above-mentioned circumstances. It is an object of the present invention to provide a conductive rubber member which has excellent processability, which is used in contact with a photoconductor without damaging the surface of the photoconductor or undergoing wear of the surface of the rubber member, which entails a low cost, which can maintain satisfactory characteristics for a long term, and which is particularly preferred for a conductive roll or blade.